Often derided (unfairly) as “dark money groups” because they are not required to disclose their donors, 501(c)(4) organizations like Our Revolution are legally permitted to engage in all of these activities under current tax law. However, a sitting U.S. senator’s involvement in such a group is unusual and raises several knotty campaign finance and congressional ethics issues.

The campaign finance laws explicitly recognize only two types of “political committees” that may be “established, financed, maintained or controlled” by a federal candidate or elected official: a campaign committee and a leadership PAC. Both are subject to contribution limits and source prohibitions that generally do not apply to 501(c)(4) groups.

Any other type of entity that is established, financed, maintained, or controlled by a federal candidate or officeholder is also subject to federal contribution limits and prohibitions if it engages in any activity “in connection with an election for federal office,” certain federal election activities, or even activity in connection with state or local candidate elections.